The subject of this invention is signal processing circuitry. More particularly this invention comprises a circuit of the type which is capable of tracking or locking onto several different signals of different frequencies which may exist simultaneously in a composite signal applied to the processor. Circuits of this type are useful, for example in analyzing radar echo signals which often comprise numerous target signals of different and varying frequencies mixed with noise. These different signals might be Doppler shifted echo signals representing different targets all of which may be moving at different and changing radial velocities and hence producing correspondingly changing Doppler echo signals. This processor comprises multiple similar stages, each stage being capable of locking onto and tracking one of the frequency components of the composite input signal and passing the remaining portion of the composite signal to succeeding stages, each of which is capable of locking onto one of the remaining frequency components. Each of the stages comprises a frequency locked loop plus some form of tunable trap or frequency stop circuit.